Mamiya 90mm f/3.8 Sekor C Lens for RB67 {77}

Mamiya 90mm f/3.8 Sekor C: the RB67's workhorse normal lens

On a medium format 6x7 frame, 90mm lands close to a true normal field of view, which makes the Sekor C 90mm f/3.8 the lens that stays mounted most of the time for RB67 shooters. The f/3.8 maximum aperture is fast enough to separate a subject from its background on a large negative, and the 77mm filter thread gives you access to a wide range of polarizers and graduated NDs without hunting down specialty glass.

Mamiya built the Sekor C line specifically for the RB67 system, so the leaf shutter integration is built in, every aperture setting syncs at full flash sync speed, which matters the moment you're mixing ambient light with strobes. The 6x7 negative this system produces is large enough that even moderate enlargements retain grain structure and tonal gradation that smaller formats simply don't deliver at equivalent print sizes.

For anyone already shooting the RB67, this focal length fills the gap between the wide 65mm and the short telephoto 127mm. It's the lens you reach for when you haven't decided what the shot needs yet, and it ends up being right most of the time.

Who It's For

Portrait photographers working in natural light will find the 90mm focal length flattering on a 6x7 frame, with enough working distance to stay off a subject's personal space. Studio photographers gain full flash sync at every aperture through the leaf shutter, making controlled lighting setups straightforward. Documentary and travel photographers who shoot on medium format will use this as their go-to focal length for environmental work. Film photographers making the move from 35mm to the RB67 system will recognize 90mm as a natural starting point before expanding into the rest of the Sekor C lineup.

Key Features

• 90mm focal length delivers true normal field of view on 6x7 frame
• f/3.8 maximum aperture enables subject separation on large negatives
• Mamiya Sekor C mount optimized for RB67 camera system
• Leaf shutter with full flash sync at every aperture
• 77mm filter thread for polarizers and graduated NDs
• Medium format optics retain grain and tonal detail at enlargement

FAQ

Is 90mm a true normal lens on the RB67's 6x7 frame?

Yes. On a 6x7 negative, 90mm delivers the field of view equivalent to roughly 50mm on 35mm film, making it the system's standard focal length for general shooting.

Can I use this lens with flash indoors?

Fully. The leaf shutter syncs flash at all apertures, so you can mix strobes with ambient light without stopping down or worrying about sync speed limitations.

What's the practical difference between the f/3.8 and faster alternatives?

The f/3.8 aperture gives enough subject separation on large negatives to work for most portraiture and product work. If you need shallower depth of field or significantly faster shutter speeds, faster focal lengths in the RB67 system offer that trade-off.

Does the 77mm filter size match other RB67 lenses?

No. The 65mm and 127mm lenses use different filter threads, so you'll need dedicated polarizers and ND filters for the 90mm unless you use step-up rings.

How does this lens perform at maximum aperture?

Medium format leaf shutters like Mamiya's are optically clean at full aperture. You get usable contrast and sharpness at f/3.8 without the optical compromises you'd see in some fast SLR glass.

Is this lens better for studio or field work?

Both. The normal focal length works equally well for controlled studio lighting or handheld outdoor shooting. The fast leaf shutter makes it genuinely flexible for mixed-light situations.